WO2017076901A2

WO2017076901A2 - Method for creating surface effects, in particular in uv-curable layers, device for making same, and article obtained according to the invention

Info

Publication number: WO2017076901A2
Application number: PCT/EP2016/076421
Authority: WO
Inventors: Roland Rüedi; Dirk Dr. SCHLATTERBECK; Peter Eladio LUDWIG
Original assignee: Schmid Rhyner Ag
Priority date: 2015-11-02
Filing date: 2016-11-02
Publication date: 2017-05-11
Also published as: EP3370886A2; CN108348955A; RU2718932C2; DE102016120878A1; BR112018008465A2; RU2018120210A; BR112018008465B1; RU2018120210A3; WO2017076901A3; ZA201802903B

Abstract

The invention relates to a method for creating surface effects in a coating that is curable by high-energy particle radiation, in particular UV light, said method involving the following steps: applying a coating fluid, e.g. a paint, which is radically curable, in particular UV-curable, to a substrate, said coating fluid being designed such that the reactivity on the surface of the applied coating film differs specifically from the reactivity in the volume of the applied coating film; irradiating the coating with high-energy particle radiation. Also disclosed are devices, in particular for carrying out said method.

Description

Process for producing surface effects, in particular in UV-curable

Layers, apparatus for producing the same and inventively obtained articles

Description: FIELD OF THE INVENTION The invention relates to a method for producing surface effects, in particular in UV-curable layers, by means of microfiltration, as well as to a device for producing such layers and to an article obtained according to the invention.

Another aspect of the invention relates to the provision of high energy

Particle radiation, for example UV radiation, curable coating fluids, which are processable by the method according to the invention.

Background of the Invention The curing of organic polymerizable coatings by means of high energy particle radiation, such as UV radiation, has been an industrially controlled process for many years. In particular, it is also known how a dull or glossy surface can be produced by the choice of a suitable coating system. In the context of the present invention, the specification of the gloss of a lacquer or of a lacquered surface in accordance with DIN 67 530 or ISO 2813, wherein the indication of the gloss units takes place under consideration of the corresponding surface at an angle of 60 °. A high-gloss surface is correspondingly referred to as a surface which has between 70 and 100 GE (GE = gloss units), as a silk-gloss surface with 45 to 70 GE, as a satin finish a surface between 20 to 45 GE. A matte surface has less than 20 GE. Difficulties arise, however, when using a coating system both matt and shiny areas are to be generated simultaneously, for example, to identify specific functional areas of a surface. It is also known to produce surfaces which have certain structures or a specific feel, that is to say a special tactile sensory impression. Even with these effects, however, the simultaneous production of areas with different visual or structural expression with one and the same coating system is currently only possible with a high expenditure on equipment. The generation of different haptic and / or visual properties, such as matt / gloss effects with one and the same coating system can be done in different ways. A simple possibility consists in the coating on a partially differently pretreated substrate. An example of this is the UV coating of a substrate previously pretreated with a poorly wettable oil pressure varnish or a special printing ink. The subsequent coating produces in this case on the pretreated areas a repulsion of the coating and thus a matte finish.

This effect is known in Asia as "chemical embossing." In Europe, this method is referred to as "drip-off coating".

On the subsequent regionally different treatment of a homogeneous film by means of a template is known. In the application usually undesirable, but the expert is quite familiar and the variation of the degree of matting within matt-coated surfaces as a function of the layer thickness. For example, matting agent particles sometimes no longer appear on the surface in thicker lacquer layers, whereby the film appears less dull in these areas. This effect can also be used specifically.

Also known are processes in which coatings are matted by acting on the surface of the resulting coating film after the order has been completed. in the In the simplest case, this can be done by etching or sandblasting. Again, a pattern on the surface can be generated by means of a template.

A similar effect can also be produced in a still liquid coating before hardening, if the (partial) generation of a roughness succeeds with the help of high-energy radiation.

For example, German Patent Application DE 10 2006 042 063 A1 describes a method for adjusting the degree of gloss of surfaces which have been obtained by coating with UV or electron beam-curable coatings. In this case, initially short-wave monochromatic UV radiation acts on a coating applied to a substrate, so that polymerization and crosslinking occur only in the surface layer of the coating. In a second step, electromagnetic radiation of a different, higher wavelength acts on the coating, with the result that crosslinking occurs over the entire thickness of the applied coating and the layer cures accordingly. In this way, in the surface layer caused by the thus-induced crosslinking a micro-folding, which is fixed by the subsequent curing of the entire layer. By suitable choice of the curing parameters can be produced in this way by means of a coating system both high gloss and matte surfaces. In the context of the present invention, the term "microfolding" is understood to mean the following phenomenon: the surface layer of a coating fluid applied in a first step becomes a skin-like layer, this means a layer with a

hardened harder or tougher near the surface. Due to the shrinkage during curing, this surface layer contracts during curing. This leads to a structuring, which requires that at least in a partial area of the

Coating surface is a local change in the coating thickness, so that the thickness variations are at least in the single-digit micrometer range. In particular, the surface layer may be present folded. In a second step, the applied coating fluid is cured over the entire volume.

As sources of monochromatic radiation, which is able to cause the microstructure by crosslinking of the surface layer, find it excimer radiators use. In particular, monochromatic radiation of the wavelengths 172 or 222 nm is used.

A disadvantage of the use of excimer emitters for the microfolding, however, is that in order to ensure a uniform matting, the irradiation must be carried out under an inert gas atmosphere, since known for free-radically curable coatings oxygen inhibition impairs the desired reaction at the surface. For example, international patent application WO 2007/068322 A1 describes a device which is suitable for carrying out a method for microfolding of UV-curable coatings, in which the

Irradiation conditions remain stable. For this purpose, the beam sources are designed so that a stable inert gas atmosphere is ensured and the inert gas is used simultaneously for cooling the radiator, so that the life of the excimer lamps is extended.

A further development of the aforementioned methods is described in European Patent Application EP 2 418 091 A1. Here, a method is described in which it comes only in some areas of the paint surface to a micro-mapping, while in other areas of the paint surface is obtained a smooth surface. For this purpose, the paint surface is acted upon only in the appropriately selected subregions with the necessary for micro-short-wave electromagnetic radiation, for which the beam source is provided with a template or mask, so that it comes only to the desired only partial exposure of the surface. In this way, a coating is obtained which has at least one area with a matt or micro-folded surface and at least one area with a smooth surface, wherein the areas do not differ or only insignificantly with regard to their layer thickness.

For the method described in EP 2 418 019 A1, too, excimer radiation is used to generate the micropositioning.

The mechanism of the microplating described in the abovementioned industrial property applications is based on the combination of a low penetration depth of the radiation and thus a near-surface action with the property of the free-radically curable system to undergo a curing shrinkage in the polymerization reaction. Through these two effects a film floating on still liquid coating material is produced, which folds through the hardening shrinkage. In the case subsequently carried out second

Hardening step, the still liquid intermediate region is also cured and combines with the substrate and the folded surface film.

The known methods for the production of micro-folded matte surfaces or

Surfaces which have special optical effects or a certain tactile sensory impression thus have the overall disadvantage that an excimer radiator must necessarily be used to produce the micro-folded structure. Even if, as described in EP 2 418 019 A1, it would also be possible to use light of up to 300 nm to generate the microstructure, a monochromatic light will nevertheless always be used

Required light source, which is also different from the second light source, which is necessary for complete curing of the coating. This is due to the fact that the excimer radiation is strongly absorbed in coating solutions or paints, so that it comes only to the curing of a thin film, for example, only a few micrometers in thickness. If the paint layer is thicker than the depth of penetration of the total

Laser radiation corresponds, is therefore for the curing of the paint layer over the entire thickness of the use of a second radiator with a different wavelength for this

Volume hardening necessary. This leads to complex procedures with a lot of equipment.

Thus, there is a need for a low-cost, simplified process for producing surface effects in coatings by micro-compaction, in particular for processes with which these surface effects are only partially introduced into the coating. Furthermore, different optical and / or tactile sensory effects are to be achieved in different areas of a surface of a coating.

Object of the invention The object of the invention is to provide a method for simplified, low-cost matting of paint surfaces by micro-mingling, in particular a method with which only partial areas of a surface selectively matted or optical or tactile sensory Properties can be provided. In one development of the invention, different surface effects in different areas of a coating can be addressed, wherein the layer thickness of the coating between the individual areas can be different.

Further aspects of the invention relate to devices for carrying out the

method according to the invention and also products produced in this way and

Coating fluids which are amenable to such a process. Summary of the invention

The invention is solved in a surprisingly simple manner by a method according to claim 1, devices according to independent claims 19 and 23, and a coating fluid according to claim 24. Another aspect relates to products with micro-folded surfaces according to claim 29 produced in this way. Preferred embodiments can be found in the respective subclaims.

The method for producing surface effects in a coating which is curable by high-energy particle radiation, in particular by UV radiation, comprises the following steps:

In a first step, the application of a coating fluid, for example a lacquer which is free-radically curable, in particular UV-curable, is applied to a support. Here, the coating fluid is designed so that the reactivity at the surface of the applied coating film is specifically different from the reactivity in the volume of the applied coating film.

- In a second step, the irradiation of the coating takes place, wherein preferably UV-C radiation having a wavelength of 240 nm and more is introduced into the surface layer of the coating.

The method is thus based on the same principle of microfolding, as well as by excimer radiation and subsequent post-curing by longer-wave UV radiation or Electron radiation is achieved. The advantage of the method according to the invention, however, is that the surface reactivity is deliberately set differently to the volume reactivity. In this way it is possible, with longer-wave UV radiation than the above-mentioned excimer radiation, for example UV-C radiation of a commercially available medium-pressure mercury radiator, to produce a microfilling on the surface. The targeted

differently set reactivity of the surface of the applied coating film to that of the volume further leads to the effect being layer thickness-dependent. Thus, thin layers remain shiny in the process of the invention, whereas thicker layers are matted.

Another advantage of the method according to the invention is that the curing reaction of the surface and the volume is initiated with the usual in the industry mercury medium-pressure lamps. As a result, the user does not have to make additional investments or make modifications to his system.

The effect according to the process is based on adapting the composition of the coating fluid such that the reactivity on the surface of the applied coating film differs specifically from the reactivity in the interior of the applied coating film. This is achieved by adding to the coating fluid two different photoinitiators which act differently, in particular in the form that a

Photoinitiator the reactivity in a near-surface zone of the applied

Increases coating film and another photoinitiator increases the reactivity inside the applied coating film.

In the prior art UV curing processes, photoinitiators have been used to date. However, so far the problem arises that at a

Processing of such UV-curing or coating fluids under normal conditions, i. not under inert gas, the chain reaction initiated by the photoinitiators is inhibited by oxygen. This causes a near-surface zone of the applied

Coating film hardens less than its volume and corresponding to the surface the lacquer layer has only a low hardness or possibly is still completely liquid.

To overcome these difficulties, the prior art proposes two solutions:

- Processing under inert conditions, so as to avoid the problem of competing reaction of the radicals formed with oxygen, or

- An increase in the content of photoinitiator. Both solutions have disadvantages. For example, curing under inert conditions leads to increased expenditure on equipment. If, on the other hand, the content of photoinitiator is increased, the risk of migration of this photoinitiator from the cured coating increases at the same time, which is particularly critical in the case of food packaging. The increased migration is due to the fact that experience has shown that not the entire photoinitiator is reacted, but always remain unreacted components. Since the photoinitiators used are usually small, mobile molecules, these particles remaining in the cured film can migrate out of the film and, in the case of packaging, pass over to the contents. Furthermore, in this way it is merely ensured that the near-surface zone and the interior of the applied lacquer layer are substantially uniformly cured, ie the near-surface zone has almost the same degree of crosslinking as in the interior of the lacquer layer. On the other hand, a stronger and earlier crosslinking of the near-surface zone compared to the interior of the lacquer layer, which causes a microfolding, is not possible with the abovementioned solutions.

In order to achieve earlier curing of the near-surface zone of the applied paint film, so far the use of an excimer radiator is necessary. The

Surface reaction, which is achieved using excimer radiation, based on the fact that by this radiation, for example, directly the reactivity of the

polymerizing acrylate monomer is addressed. However, the absorption of the excimer radiation decreases exponentially with increasing penetration depth, so that in this way only the near-surface zone can be cured. For a reaction in the interior of the applied lacquer layer, however, the irradiation with UV light continues to be higher

Wavelength necessary. Thus, with the known methods of the prior art, which take place in two stages using excimer radiation and a second, beam source of higher wavelength, although a targeted hardening of the near-surface zone under

Training of microfolding possible. As already described above, these lead

Procedure but also to an increased expenditure on equipment.

Of the methods of the prior art, the invention differs

Process thus also by the fact that substantially lower energy radiation than hitherto for the microfilling of the surface layer of the coating and thus for the production of

Surface effects is necessary. For example, UV radiation with a wavelength of 240 nm and more is already sufficient for the production of the microfolding, while previously excimer emitters were used with the wavelengths 172 nm and 222 nm, with only the wavelength of 172 nm is suitable without the use from photoinitiators to generate radicals. Such complex devices are no longer needed in the process of the invention. Rather, it is possible with the method according to the invention to use other beam sources. According to one embodiment of the invention, the surface layer comprises thicknesses between 10 nm and 1 μm

According to one embodiment of the invention, the irradiation is carried out in two steps in the form that in the first step a smaller UV dose is irradiated, the micro-generation generates, and in a second step, the film is completely through-hardened, for both curing steps longer-wave UV radiation, for example that of a medium pressure UV radiator is used.

According to a further embodiment of the invention, however, it is also possible for both the micro-aging and the curing of the film to be achieved in an irradiation step. For this purpose, the coating material is designed accordingly, in particular by the absorption of UV radiation over the layer thickness of the coating agent varies. According to one embodiment of the invention, both the generation of the micro-cladding in the surface layer and the irradiation for curing the coating are effected in each case by means of a medium-pressure mercury radiator.

In a further embodiment of the invention, a, preferably the same, medium pressure mercury radiator is used both for the irradiation of the surface layer and for the curing of the coating. In this case, the adjustment of the dose of UV radiation by adjusting the power of the medium-pressure mercury radiator takes place.

According to a further embodiment of the invention, the coating can be carried out in the form that a coating film is obtained, which has different layer thicknesses in certain areas. In these areas, each with different layer thickness different effects can be obtained.

This is advantageous, for example, if the feel of the coating is important, for example, if certain areas of the coating should already be recognizable by contact. Also, it is advantageously possible in this way, very attractive optical

To realize embodiments of a coated product.

According to yet another embodiment of the invention, the application of the coating takes place only on parts of the substrate, so that at least one area of the substrate is uncoated and at least one other area of the substrate is coated. According to a further embodiment of the invention, the application of the coating takes place over the entire surface of the substrate, wherein furthermore the layer thickness can be different in different areas.

The irradiation of the surface layer preferably takes place over the entire surface. The

Generation of locally different effects in terms of gloss and feel is achieved by the previous generation of different layer thicknesses in the different areas. Thus, in areas of layer thicknesses between 1 μιη and 10 μιη example, a smooth Surface obtained without micro-conditioning, whereas in areas with layer thicknesses above 12 μιη the micro-folding takes place.

According to a further embodiment, the irradiation takes place in at least one subarea in such a way that only in this subarea treated in this way are surface effects due to

In the at least one untreated portion of the surface there is a smooth, non-micro-folded surface.

According to a preferred embodiment of the invention, the only local irradiation of the surface layer for microfilling takes place in at least one subregion through a mask or stencil which shades regions of the emitter, or by means of a spatially resolved scanning of the coating surface.

Preferably, the scanning is carried out by scanning the surface line by line and further the line is divided into individual pixels or pixels and each line is associated with each feed of the scan head.

According to yet another embodiment of the invention are various

Surface effects in different areas of the coating before.

The irradiation is preferably carried out by UV radiation under an inert gas atmosphere, preferably a nitrogen atmosphere. In this case, the residual oxygen content is preferably less than 5000 ppm, particularly preferably less than 1000 ppm or very particularly preferably less than 500 ppm. Preferably, the application of the coating fluid by means of a printing process, for example by gravure, flexographic printing, screen printing, pad printing or inkjet printing, or by rolling, flooding, knife coating, casting, such as curtain or slot casting, dipping spraying and / or spin. Particularly preferably, the coating agent inkjet technology is made. With this method, it is particularly easy to different layer thickness of

Coating material in different areas on the surface in one pass too produce. For example, here by appropriate screening and the order only very small layer thicknesses, preferably less than 2 μιη, and taking into account that the applied droplets do not converge, take place a coating order with matte surface. In areas with layer thicknesses in which the drops combine to form a film but the layer thickness is below a critical threshold, the surface appears shiny and in areas above this critical threshold a matte effect is again achieved by the microstructure. At the same time, all these three different areas have a different feel. The haptic is not only differentiated by the different layer thicknesses (relief effect, Braille structures, replacement of blind embossing by coating application), but also by a changed frictional resistance of the different areas. Micro-folded areas are characterized, for example, by a very small amount

Friction resistance, whereas very smooth areas can be almost sticky when passing by hand. In contrast, very thin matte structures, in turn, have a low frictional resistance, but, in contrast to the areas with a microplate, are rather rough, whereas microfolded areas feel very smooth and soft.

According to a further embodiment of the invention, the degree of gloss of the coating at a viewing angle according to DIN EN ISO 2813 in the areas in which exposure of the surface layer for microplating takes place after hardening of the entire layer is between 0.1 GE and 80 GE. The degree of gloss is preferably between 0.1 GE and 50 GE, more preferably between 0.1 GE and 20 GE and most preferably between 0.1 GE and 10 GE, this gloss level being determined in accordance with DIN EN ISO 2813.

The invention further relates to a device for curing coating fluids, for example paints, which are curable by high-energy particle radiation, in particular by UV radiation. The curing takes place in two steps and, furthermore, the power introduced into the coating by means of the curing device is adjusted so that in a first step only the surface layer of the coating is treated, and in a second step the coating can be cured over the entire layer is.

Preferably, the curing device comprises a medium pressure mercury radiator. A possible embodiment of the invention includes the design of the curing device so that the curing by means of excimer emitters under the curing

Inertgasatmosphäre takes place. The inert gas is preferably nitrogen. The inert gas atmosphere may help to aid in less well suited coating solutions since the abovementioned oxygen inhibition, even with appropriate formulation, interferes with the reaction at the surface. If this impairment is reduced under inert gas, the surface reaction can proceed more efficiently and thus the micro-folding can be supported.

According to one embodiment of the invention, the device for curing the layer is formed such that initially only in a partial region of the coating

Surface layer is exposed and continue the curing of the coating over the entire surface of the coating takes place. In this way, only at least one subregion of the coating is present with a micro-clipping of the surface, while at least one other region of the coating has a non-micro-folded, smooth surface.

Preferably, the apparatus comprises a computerized means for controlling the curing of the coating. In particular, the informatic means is designed to determine the performance, dose and / or location of the cure. Yet another aspect of the invention relates to an apparatus for generating

Surface effects on at least a portion of a coated with a coating which is curable by high-energy particle radiation, in particular by UV radiation, coated base, which comprises a device according to the invention for curing coating fluids as described above. The device comprises:

Preferably a device for receiving the base,

a means for transporting the support between the individual workstations,

a device for applying the coating fluid to the substrate, wherein the device may be designed in such a way that the coating fluid is applied over the entire area of the surface of the substrate or only over a partial area thereof, - A device (6) for curing the coating, wherein the curing takes place in two steps and the introduced by means of the curing device in the coating power is preferably adjustable so that in a first step, only the surface layer of the coating is treated the surface layer preferably has a thickness between 10 nm and 1 μm, and in a second step the coating can be cured over the entire thickness,

- Preferably, a device for removing the pad, as well

- Preferably a system control, for example in the form of an informational means such as a computer, for controlling the operations of the system, which controls the parameters on all process steps and their

Ensuring interaction.

The plant controller also preferably includes means to read out parameters in an informational format commonly used in the printing industry, for example JDF (Job Definition Format), and to translate them into process steps. By way of example, such a means may comprise a parameterization file stored in a memory.

According to a further embodiment of the invention, the device comprises at least one sensor as well as an encoder and actuators in order to detect the respective method steps by sensors and to implement them in a controlled manner by the computer by means of corresponding actuators.

Yet another aspect of the invention relates to a coating fluid suitable for carrying out the method according to the invention. This is a

Coating fluid which curable by high-energy particle radiation, in particular by UV radiation, in particular by free-radical polymerization, and a

Micro-folding process is accessible. The microfolding is carried out by irradiation of the surface layer of an applied coating, for example by irradiation with UV-C radiation having a wavelength of more than 240 nm. Generally, a coating fluid suitable for carrying out the process of the present invention comprises a composition in which 100 parts of a liquid binder comes to 13 parts of a mixture of photoinitiators and / or crosslinking agents and / or activators for curing.

In the context of the present invention, photoinitiators are substances which decompose by absorption of light, in particular UV light, and thus form reactive species, for example radicals or cations. According to one embodiment of the invention, photoinitiators are used which form radicals.

Crosslinking agents and / or activators are understood in the context of the present invention to be substances which make polymerization reactions particularly efficient.

for example, by being able to form particularly effective starting radicals. Another example of an increase in efficiency is the transfer of an oxygen-inactive radical into a re-start radical. In the context of this disclosure, the activator is also a synergist in each case and can also be referred to as such. According to one embodiment of the invention, at least one tertiary amine is used as crosslinking agent or activator. This is preferably done according to another

Embodiment of the invention, when a so-called type II photoinitiator is used as the photoinitiator. In a type II photoinitiator, radicals are formed by the photoinitiator, for example benzophenone, an adjacent molecule

Hydrogen atom withdraws. In contrast, in type I photoinitiators, the radicals are formed directly by the decomposition of the initiator molecule. An example of a type I photoinitiator is available under the trade names Irgacure 1173 and Darocur 1173, respectively, and includes 1-phenyl-2-hydroxy-2-methyl-1-propanone. Preferably, an acrylate-based binder is used. Further preferably, the mixture of photoinitiators and / or crosslinking agents and / or activators is composed so that one part of a type 1 photoinitiator, 6 parts of a type II photoinitiator and 6 parts of an activator are added. The synergist (or activator), together with Type I I photoinitiators, each overcome oxygen inhibition and are particularly useful in crosslinking under atmospheric conditions to facilitate and / or enhance surface reactivity. According to one embodiment of the invention, the coating fluid has the following

Composition on:

40 parts HDDA (hexanediol diacrylate)

10 parts of TMPTA (trimethylolpropane triacrylate)

50 parts DPGDA (dipropylene glycol diacrylate)

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts of N-methyldiethanolamine

The fact that the reactivity at the surface of the applied coating film specifically differs from the reactivity in the volume of the applied coating film is thus achieved by dissolving 1 part of a type I photoinitiator, here 1-phenyl-2-hydroxy-2-methyl-1. Propanone, 6 parts of a photoinitiator type II, here benzophenone, and 6 parts of an activator, here N-methyldiethanolamine, are used per 100 parts of a liquid binder mixture (here comprising HDDA, TMPTA and DPGDA). By varying the proportions of the Type I photoinitiator relative to the proportions of the Type II photoinitiator, further targeted discrimination of the reactivity at the surface of the coated coating film can be achieved from the reactivity in the volume of coating film applied. The term parts in the context of this disclosure in each case by weight. According to a further embodiment of the invention, the coating fluid has the following composition:

80 parts HDDA (hexanediol diacrylate)

20 parts of TMPTA (trimethylolpropane triacrylate)

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts N-methyldiethanolamine That the reactivity at the surface of the applied coating film of the

Reactivity specifically differentiated in the volume of the applied coating film is thus achieved in that 1 part of a photoinitiator of type I, here 1-phenyl-2-hydroxy-2-methyl-1-propanone, 6 parts of a photoinitiator type II, here benzophenone , and 6 parts of an activator, here N-methyldiethanolamine, are used per 100 parts of a liquid binder mixture (here comprising HDDA and TMPTA) and in contrast to the previous example, a more reactive binder mixture is used. By changing the proportions of the

Type I photoinitiators relative to the proportions of the type II photoinitiator may further target the reactivity at the surface of the coated photoinitiator

Coating film can be achieved by the reactivity in the volume of the applied coating film.

Another example of a product that can be microfilled by means of the radiation of a medium pressure mercury radiator is described below

Formulation coated:

100 parts DPGDA (dipropylene glycol diacrylate)

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts of N-methyldiethanolamine

Thus, the reactivity at the surface of the coated coating film specifically differs from the reactivity in the volume of the applied coating film achieved in that 1 part of a photoinitiator of type I, here 1-phenyl-2-hydroxy-2-methyl-1-propanone, 6 parts of a photoinitiator type II, here benzophenone, and 6 parts of an activator, here N-methyldiethanolamine , to 100 parts of a liquid binder (here comprising DPGDA) can be used. The DPGDA used as difunctional binder forms a relatively soft film. The volume shrinkage is compared with TMPTA-containing

Formulations less pronounced. By varying the proportions of the Type I photoinitiator relative to the proportions of the Type II photoinitiator, further targeted discrimination of the reactivity at the surface of the coated coating film can be achieved from the reactivity in the volume of coating film applied.

In a further embodiment, the microfolding succeeds in only one curing step. For this purpose, the coating formulation, for example, elastic aliphatic

Urethane acrylates are added. A very good reactivity at the same time very much

pronounced effect is achieved with the following formulation:

80 parts DPGDA (dipropylene glycol diacrylate)

20 parts of Ebecryl 4491 from Allnex

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts of N-methyldiethanolamine

The fact that the reactivity at the surface of the applied coating film specifically differs from the reactivity in the volume of the applied coating film is thus achieved by dissolving 1 part of a type I photoinitiator, here 1-phenyl-2-hydroxy-2-methyl-1. Propanone, 6 parts of a type II photoinitiator, here benzophenone, and 6 parts of a

Activator, here N-methyldiethanolamine, to 100 parts of a liquid binder mixture (here comprising DPGDA and Ebecryl 4491) can be used. By altering the proportions of the Type I photoinitiator relative to the proportions of the Type II photoinitiator, further targeted discrimination of reactivity at the surface of the coated one may be made

Coating film can be achieved by the reactivity in the volume of the applied coating film. Even with AC Resin 250 from BASF similar effects can be achieved.

All of the formulations mentioned are basic formulations which, in order to achieve processability, can be supplemented with corresponding flow and wetting additives. However, this additive has no influence on the achievement of the desired effects. In addition, a layer thickness of at least 12 μm is necessary for achieving the microfolding. In a range between 10 and 12 m, the microfolding is formed only irregularly (see Figure 1). Below 10 μιη the surface each remains shiny.

The above formulations are all characterized by a very low

Processing viscosity (from 70 - 120 s in the DIN 2 flow cup), which allows their use in inkjet printheads. In this case, advantageously, a method can be used which allows the simultaneous generation of areas of greatly varying layer thicknesses.

However, the effect of microfiltration is in no way dependent on the viscosity. It is also possible to produce much higher viscosity formulations that can be applied by other methods. It is important to obtain a relatively higher reactivity at the surface than in the volume. The photoinitiators used must be hers

Have absorption maximum in the UV-C range.

The effect of microfolding can be prevented by increasing the formulation

Concentrations of photoinitiators for volume hardening are added (eg> 2% Irgacure 1173 with otherwise equal concentrations of photoinitiators and coinitiators in the formulation can prevent the effect). The same applies if, for volume hardening, photoinitiators with a higher absorption wavelength are used in suitable concentrations. Thus, by adding 1% TPO (triphenylphosphine oxide) in the above-mentioned formulations, the micro-folding can be prevented. The percentages in each case relate to percent by weight. Yet another aspect of the invention relates to a product which consists of a backing and a coating applied thereto. This shows the coating at least in a partial area on a surface layer with a microcold on and the coating is formed from

40 parts HDDA (hexanediol diacrylate)

10 parts TMPTA (trimethylolpropane acrylate)

50 parts DPGDA (dipropylene glycol diacrylate)

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts of N-methyldiethanolamine and / or

80 parts HDDA (hexanediol diacrylate)

20 parts TMPTA (trimethylolpropane acrylate)

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts of N-methyldiethanolamine and / or

100 parts DPGDA (dipropylene glycol diacrylate)

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts of N-methyldiethanolamine and / or

80 parts DPGDA (dipropylene glycol diacrylate)

20 parts of Ebecryl 4491 from Allnex

1 part Irgacure 1173 (or Darocur 1173)

6 parts benzophenone

6 parts of N-methyldiethanolamine. Suitable substrate materials for backing the coating may be conventional materials used in the graphic arts industry, such as paper, paperboard, laminated paper or laminated paperboard, plastic films, and corrugated board substrates. Polyolefin films but also PET, acetate and similar films are preferably used for the lamination.

Especially the change in haptics by the micro-folding, which can cause a reduction of the sliding friction by preventing the so-called glass plate effect, makes the method but also for completely different applications outside the graphic industry interesting. These include coatings with low

Friction resistance for aviation but also for watercraft. The adhesion of dirt, lime and bacteria on such surfaces is reduced compared to smooth surfaces.

The micro-folding in combination with specially flexible or even elastic binders can be used for the production of so-called soft-touch paint surfaces.

Further preferably, the degree of gloss in the at least one region which has a microfolding is between 0.1 and 80 GE, preferably between 0.1 GE and 50 GE, more preferably between 0.1 GE and 20 GE, and very particularly preferably between 0 , 1 GE and 10 GE, at a viewing angle according to DIN EN ISO 2813.

By a suitable choice of the coating materials, it is also possible to produce an ice-flower-like effect or the appearance of a broken safety glass pane instead of microfilling by the method according to the invention.

DESCRIPTION OF THE DRAWINGS FIG

1 to 3 different photographic images of samples with different levels of microfolding, 4 and 5 devices for producing surface effects of substrates according to embodiments of the invention,

Fig. 6 shows a process according to the product, and

7 to 13 are photographic representations of coatings according to

Embodiments of the invention.

Detailed description of preferred embodiments

In the following detailed description of preferred embodiments, for the sake of clarity, not all features of a respective device are shown in FIGS. 4, 5 and 6

shown to scale. Furthermore, the term high-energy particle radiation is also used in general form for photons. Especially in the ultraviolet spectral range and in general towards shorter wavelengths, photons show increasing particulate character.

1 shows an example of a photographic image of a sample in which a coating agent which is accessible to the microstructure was applied only with a layer thickness of 10 μm. It can be seen that the microfolding is only irregular. Thus, in the left-hand section of the figure, a microfolding is clearly recognizable, whereas this microfolding in the right-hand region of the sample is only slightly or not at all pronounced.

Fig. 2 shows an example of a photographic representation of the surface of a sample, which was obtained by the method according to the invention. The layer thickness is here 30 μιπ The micro-mapping is very pronounced here.

FIG. 3 shows a strong enlargement of a surface area of the sample from FIG. 2. Here, too, the structures produced by microfolding are very clearly recognizable.

FIG. 4 shows a schematic representation of an embodiment of a device 1 for producing surface effects on at least one subregion of a with a

Coating, which is curable by high-energy particle radiation, in particular by UV radiation, coated underlay, the device comprising: It can be seen in Fig. 4, a means for transporting the pad 3 between the individual workstations. This means of transport is exemplified in the apparatus 1 by the parts 21, 22 and 23 and comprises a first roller or roller 21 on which a substrate 3, for example formed from paper, cardboard, laminated paper or laminated cardboard , Plastic films and Wellpappesubstraten, or polyolefin film or PET or acetate film, is rolled up.

The base 3 is moved in the direction of the arrow 25, the transport direction, through the device 1, wherein the surface 31 of the printing material or the substrate or the base 3, which is to be printed, is directed in Fig. 4 upwards. The roller 22 is another part of the means of transport.

Furthermore, the device 1 comprises a device 4 for applying the coating fluid to the substrate 3. A device for applying coating fluid is described, for example, in WO 2009/012996, the disclosure content of which is also the subject of the present disclosure by incorporation, as the coating unit Although the device described in the present invention is advantageously usable for smoothing the film applied to the substrate surface by means of the coating unit, it represents an optional unit which does not necessarily have to be used for carrying out the invention.

The device 4 can be configured such that the coating fluid is applied over the entire area of the surface 31 of the substrate 3 or only over a partial area thereof. A job over the entire area of the surface 31 of the substrate 3 is advantageous when a coating fluid is applied, which also performs a protective function in the cured state, for example having scratch-resistant properties. In contrast, only a partial application, that is to say an application of the coating fluid over only a partial area of the surface 31 of the base 3, is advantageous in order, for example, to highlight or mark specific areas of the base in a targeted manner. In this way it is also possible to generate images, for example in the form of images or texts. The device 1 further comprises a device 7 for curing the coating. The curing of the coating takes place in two steps. The power introduced into the coating by means of the curing device 7 is preferably adjustable so that in a first step only the surface layer of the coating is treated. In this case, the surface layer preferably has a thickness of between 10 nm and 1 μm. In a second step, the coating is curable over the entire thickness. Preferably, the

Device 7 a computerized means for controlling the curing of the coating.

In particular, the informatic means is designed to determine the performance, dose and / or location of the cure

Furthermore, a device 6 for drying the coating is shown in FIG. By means of this device, it is possible in a first step to remove volatile constituents of the coating fluid before curing. However, such a device 6 is only optionally included in the device 1. Furthermore, the device 1 may comprise a device 8 for cooling the coated base after curing.

The device 1 may further comprise, according to a preferred embodiment of the invention, a plant controller 5, for example in the form of an informational means such as a computer, for controlling the operations of the plant, which preferably sensory collects the relevant parameters in all process steps and preferably with respective associated actuators controls and thus ensures their interaction.

The system controller 5 preferably also comprises a means for setting parameters in one

computer format, which is commonly used in the printing industry, for example, to read JDF (Job Definition Format) and implement it in process steps. By way of example, such a means may comprise a parameterization file stored in a memory. It is also possible that the device 1 generally, without being limited to the embodiment shown here, comprises a plurality of system controls, which selectively control individual devices. According to a further embodiment of the invention, the device comprises at least one sensor as well as an encoder and actuators in order to detect the respective method steps by sensors and to implement them in a controlled manner by the computer by means of corresponding actuators.

The system controller 5 is preferably suitable according to one embodiment

Interfaces, for example, the interfaces 54, 55, 56, 57 with devices, which are covered by the device 1, for example, the devices 4, 5, 6, 7, connected.

FIG. 5 shows a further schematic representation of a device 1 according to a further preferred embodiment. The device 1 in this case comprises a device for receiving the pad 301, in which various documents 3, which are not all designated for better clarity, are included. From the device 301 for receiving the pad 3 are individual documents 3, which may comprise, for example, paper, cardboard, laminated paper or laminated cardboard, plastic films and corrugated cardboard substrates, or polyolefin or PET or acetate, by means of the means for transporting the pad 3 between the individual workstations moved through the device 1. The means for transporting the underlay 3 comprises a first roll 21, a second roll 23 and additionally a further roll 22, wherein various other rolls 22 may be included in the means for transport. Furthermore, the means for transport comprises a conveyor belt 24, which connects the two rollers 21 and 23 with each other, so that by the rotation of at least one of the rollers 21, 23, a movement of the documents 3 takes place through the device 1 in the direction of the arrow 25.

Again, the device 1 comprises the device 4 for applying the coating fluid to the substrate 3 and a device for curing the coating 7. Furthermore, the devices 6 and 8 are shown, which is the drying of the

Coating fluids or a cooling of the printed substrate can serve after curing and in the present case are only optional. The devices 4, 5, 6, 7 can each be connected via an interface 54, 55, 56, 57 with a system controller 5. Such a system controller 5 with the corresponding interfaces is also only optionally included in the device 1. Furthermore, it is generally, without limitation to the embodiment shown here, also possible that several system controllers 5 are included in a device 1, which each control individual devices 4, 5, 6, 7.

In addition, the device 1 of this embodiment comprises a device 302 for removing the pad 3.

FIG. 6 schematically and not to scale shows two products 300, each of which comprises a base 3, on whose surface 31 (not labeled) a coating 32 has been applied. The coating 32 has at least one partial area

Surface layer with a microfolding on.

In the upper area of FIG. 6, a product 300 is depicted, which comprises a full-area coating 32 on the (not designated) surface 31. In the lower part of FIG. 6, the coating 32 is applied only to partial areas of the (not designated) surface 31 of the base 3.

The invention thus relates to a method for producing surface effects in a coating which is curable by high-energy particle radiation, in particular by UV radiation, the method comprising the following steps: application of a

Coating fluids, such as a paint which is free-radically curable, in particular UV-curable, on a substrate, wherein the coating fluid is designed so that the reactivity at the surface of the applied coating film is specifically different from the reactivity in the volume of the applied coating film,

Irradiating the coating with high-energy particle radiation and devices, in particular for carrying out this method. Fig. 7 shows a photographic representation of coatings according to embodiments of the invention. These are a total of eight coatings, which were applied to a black base. The individual coatings differ from one another with regard to the exact formulation of the coating fluid and / or the layer thickness. While matt coatings are obtained in the upper area of FIG. 7, ie coatings with a rather low degree of gloss, in the lower part of FIG. 7

Coatings shown, which have a rather high gloss level. The degree of gloss is a function of the microfolding, so that, for example, in a very strong

Microplating in a given viewing angle may result in a rather dull appearance.

To better illustrate the different effects which coatings can exhibit according to embodiments of the present invention, FIGS. 8 to 13 each show photographs of individual coated samples.

8 shows a coating in which the microplating results in a structure of a larger surface area, comparable to what are known as "dry cracks" which form, for example, during the drying of originally moist soils.The coating has a relatively high gloss in addition to the described structuring.

FIG. 9 shows a coating in which the microfolding results in finer structures and overall results in a rather dull appearance.

FIG. 10 shows a further coating according to yet another embodiment of the invention. Again, a dull appearance has been obtained, in which case the coating appears even more dull than the coating of FIG. 9.

In contrast, a coating can be seen in FIG. 11, which has a very high degree of gloss, that is to say only a very low degree of microfolding has been obtained.

In Fig. 12 and 13, two samples are shown, each showing an ice-flower-like effect, so similar to the appearance of ice-coated glass. This effect is already included the coating, which can be seen in Fig. 12, recognizable, again more pronounced but seen in Fig. 13.

Thus, overall, it should be noted that with a method according to embodiments of the invention, very different optical appearances in a coating can be realized by micro-plating in a lacquer surface.

Claims

claims

1. A method for producing surface effects in a coating (32), which is curable by high-energy particle radiation, in particular by UV radiation, the method comprising the following steps:

Applying a coating fluid, for example a lacquer, which is free-radically curable, in particular UV-curable, to a substrate (3), the coating fluid being designed such that the reactivity at the surface of the applied coating film is dependent on the reactivity in the volume of the coating

specifically differentiates the applied coating film,

- Irradiating the coating (32) with high-energy particle radiation.

2. The method of claim 1, wherein for irradiating the coating UV-C radiation having a wavelength of 240 nm and more is introduced into the surface layer of the coating.

3. The method of claim 1 or 2, wherein the irradiation in two stages in the mold

takes place, that in the first step, a smaller UV dose is irradiated, the micro-generation generates, and in a second step, the film is completely through-hardened, for both curing steps longer-wave UV radiation, for example, that of a UV medium-pressure lamp is used.

4. The method of claim 1, 2 or 3, wherein in one irradiation step both the micro-setting and the curing are achieved and wherein the

Furthermore, coating material is preferably configured such that the absorption of UV radiation varies over the layer thickness of the coating agent.

5. The method according to any one of claims 1 to 4, wherein the irradiation of both the

Surface layer as well as the irradiation to cure the coating in each case by means of a medium-pressure mercury radiator.

6. The method of claim 5, wherein a, preferably the same medium pressure mercury radiator is used both for the irradiation of the surface layer as well as for the curing of the coating (32), wherein the adjustment of the dose of UV radiation by adjusting the power of mercury Medium pressure radiator takes place.

7. The method according to any one of claims 1 to 6, wherein the coating is carried out in the form that a coating film is obtained, which in certain areas

has different layer thicknesses.

8. The method according to one or more of claims 1 to 6, wherein the application of the coating (32) takes place only on parts of the base (3), so that at least one area of the base (3) uncoated and at least one other area of the base (3). 3) coated.

9. The method according to one or more of claims 1 to 6, wherein the application of the coating (32) over the entire surface of the pad (3), wherein further, the layer thickness may be different in different areas.

Method according to one of claims 1 to 9, wherein the irradiation of the

Surface layer over the entire surface takes place.

Method according to one or more of claims 1 to 9, wherein the irradiation of the surface layer takes place only in at least one subregion such that only in the at least one subarea treated in this way surface effects due to microplating are achieved while in the at least one untreated subregion of the surface a smooth, not micro-folded surface is present.

The method of claim 11, wherein the merely local irradiation of the

Surface layer for microfolding in at least a partial area by a mask or a template, which shadows areas of the radiator, or by means of a spatially resolved scanning of the coating surface.

13. The method of claim 12, wherein the scanning is carried out by scanning the surface line by line and further, the line is divided into individual pixels or pixels and each line is associated with an advance of the scan head.

14. The method according to one or more of claims 1 to 13, wherein different surface effects in different portions of the coating (32) are present.

15. The method according to any one of the preceding claims 1 to 14 wherein the irradiation is effected by UV radiation under inert gas atmosphere, preferably nitrogen atmosphere.

16. The method of claim 15, wherein the residual oxygen content is less than 5000 ppm, preferably less than 1000 ppm or more preferably less than 500 ppm.

17. The method according to one or more of claims 1 to 16, wherein the application of the coating fluid by means of a printing process, for example by gravure, flexographic printing, screen printing, pad printing or inkjet printing, or by rolling, flooding, knife coating, casting, such as curtain or Slit casting, dipping, spraying and / or spinning takes place.

18. The method according to one or more of claims 1 to 17, wherein the degree of gloss of the coating (32) at a viewing angle according to DIN EN ISO 2813 in the areas in which an exposure of the surface layer for microplating, after curing of the entire layer between 0.1 GE and 80 GE, preferably between 0.1 GE and 50 GE, more preferably between 0.1 and 20 GE, and most preferably between 0.1 and 10 GE.

19. Device (6) for curing coating fluids, which are curable by high-energy particle radiation, in particular by UV radiation, wherein the curing takes place in two steps and the introduced by means of the device for curing in the coating (32) power adjustable in such a way is that in a first Step only the surface layer of the coating is treated and in a second step, the coating over the entire thickness is curable.

20. Device (6) according to claim 19, comprising a medium pressure mercury radiator.

21. Device (6) according to one or both of claims 19 and 20, wherein the device (6) for curing the layer is formed so that only in a partial region of the coating (32) the surface layer is exposed and further the curing of the coating (32) over the entire surface of the coating (32).

22. Device (6) according to one or more of claims 19 to 21, wherein the

Device (6) a computerized means for controlling the curing of the

Coating, in particular so that the informatic means determines the power, the dose and / or the location of the curing.

23. Device (1) for producing surface effects on at least one subregion of a substrate (3) coated with a coating (32) which is curable by high-energy particle radiation, in particular by UV radiation, the device comprising:

Preferably a device (301) for receiving the base,

- A means for transporting the pad (3) between the individual

Workstations

- a device (4) for applying the coating fluid to the substrate (3), wherein the device (4) can be configured such that the coating fluid over the entire area of the surface (31) of the

Pad (3) or only over a portion of the same is applied,

- A device (6) for curing the coating, wherein the curing takes place in two steps and the introduced by means of the curing device in the coating power is preferably adjustable so that in a first step, only the surface layer of the coating is treated the surface layer preferably has a thickness between 10 nm and 1 μιη, and in a second step, the coating over the entire thickness is curable,

- Preferably, a device (302) for removing the pad (3), and

preferably a plant control (5),

wherein the device (6) for curing the coating (32) is preferably designed according to one or more of claims 19 to 22.

24. coating fluid, which is accessible by high-energy particle radiation, in particular by UV radiation, curable, in particular by free-radical polymerization, as well as a micro-folding process, wherein the micro-exposure by irradiation of the

Surface layer of an applied coating, for example by irradiation with UV-C radiation having a wavelength of more than 240 nm occurs.

25. Coating fluid according to claim 24 having a composition of 100 parts of a liquid binder to 13 parts of a mixture of photoinitiators and / or

Crosslinking agents and / or activators.

26. Coating fluid according to one of claims 24 or 25, comprising photoinitiators which form radicals.

27. Coating fluid according to one of claims 24 to 26, comprising a tertiary amine, preferably N-methyldiethanolamine or an amine-modified acrylate.

28. Coating fluid according to one of claims 24 to 26 with an acrylate-based binder.

29. product (300) which has a base (3) and an applied thereon

Coating (32), wherein the coating (32) at least in one

Partial area comprises a surface layer with a Mikrofaltungs.

A product (300) according to claim 29, wherein the support (3) comprises paper, cardboard, laminated paper or laminated board, plastic films and corrugated cardboard substrates, or polyolefin film or PET or acetate film.

31. Product (300) according to one or more of claims 29 to 30, wherein the

Degree of gloss in the at least one area which has a microfolding between 0.1 GE and 80 GE, preferably between 0.1 GE and 50 GE, more preferably between 0.1 GE and 20 GE, and most preferably between 0.1 GE and 10 GE, at a viewing angle in accordance with DIN EN ISO 2813.

32. A product (300) according to one or more of claims 29 to 31, which

at least one area having a first surface effect as a result of micro-clipping, and at least one further area having a second surface effect as a result of micro-clipping and at least one area without micro-clipping, wherein the layer thickness of the coating (32) between the individual areas is not more than 10% of one Nominal layer thickness, which corresponds to the thickness of the coating in the non-micro-folded state, deviates.

33. Product (300) according to one or more of claims 29 to 32, preparable, in particular produced, in a method according to one or more of claims 1 to 18.